1. Field of the Invention
This invention relates to a television receiver provided with a cathode ray tube having an aspect ratio of 16:9 at which a wide aspect broadcast can be received, and more particularly to a video processing circuit for processing two pictures wherein a picture having an aspect ratio of 4:3 (e.g., an NTSC system) and a picture having an aspect ratio of 16:9 of a wide aspect broadcast can both be displayed at the optimum aspect ratio in a television receiver by digitalizing and processing the video signal.
2. Description of the Related Arts
Recently, with the multi-purpose use of television receivers, the displayed picture is being widened. For example, a wide aspect television receiver (which shall be abbreviated as a wide aspect television hereinafter) for receiving satellite broadcasts (e.g. a hi-vision broadcast), wide aspect broadcasts (e.g. HD-MAC and PAL Plus), and general broadcasts (e.g. an ordinary NTSC system broadcast) as compatible with each other is noted.
As is well known, this wide aspect television is provided with a displayed picture (CRT) having an aspect ratio of 16:9 so that the audience may effectively obtain a present feel or pressing feel. Such conventional systems not only display a picture having a video having a 16:9 aspect ratio that is characterized by the hi-vision broadcast using a MUSE-NTSC converter or the like, they also display pictures of a video of the current broadcast having a 4:3 aspect ratio using the NTSC system. Additionally, an expanding function for expanding and displaying the video of the current broadcast having a 4:3 aspect ratio on the entire displayed picture surface of 16:9, and various functions of displaying the video having a 4.3 aspect ratio on the display picture surface having a 16:9 aspect ratio have been suggested.
With the well known digitalization of the video technique, a digital television receiver for processing a video signal using a digital signal has prevailed. For example, the functions of improving the picture quality by digitalizing the video processing circuit, displaying such pictures as parent and son pictures (two pictures display), displaying multi-pictures, and reproducing stationary pictures by applying memories have also become well known.
Thus, with the digitalization of the video technique, the wide aspect television can be provided with various functions. For example, by video-processing an analog signal (e.g. a broadcast signal) into a digital signal, that processed signal is expected to coexist with the hi-vision broadcast, satellite broadcast or current broadcast of the NTSC system.
Therefore, an example of block diagram of such wide aspect television is shown in FIG. 3.
FIG. 3 is a block diagram showing an example of block diagram of a conventional wide aspect television.
As shown in FIG. 3, the reference numeral 100 represents an input terminal which a broadcast signal of the NTSC system is fed. The video signal input from this input terminal 100 is fed to a video processing circuit 101 formed of at least video intermediate frequency amplifying and video detecting circuits (not illustrated), is converted to an intermediate frequency signal, and is taken out. Then this video signal is separated into a luminance signal Y (which shall be abbreviated as a Y signal hereinafter) and a chroma signal and then the chroma signal is demodulated to color difference signals (R-Y, B-Y).
The Y signal and color difference signals demodulated by the video processing circuit 101 are fed as analog signals to an A/D converting circuit 102 where they are converted to digital signals. The output signals of this A/D converting circuit 102 are fed to a time axis compressing circuit 103 that compresses the input signals at a predetermined compressing rate. After the digital signals are compressed at the predetermined compressing rate, they are fed to a D/A converting circuit 104. The digital signals compressed by the time axis compressing circuit 103 are converted to analog signals by this D/A converting circuit 104 and are fed to a video processing circuit 105. Then, the video signals compressed in the time axis are processed in the video by a video processing circuit 105 as in an ordinary television receiver, and the respective color difference signals and Y signal are added to obtain R (red), G (green) and B (blue) signals by matrix circuit 106. A CRT 107 is driven to display the picture compressed in the time axis with an aspect ratio of 16:9.
Now, considering the relationship between the compressing rate of the time axis compressing circuit 103 and the video displayed in the picture in the CRT 107, when an NTSC input video signal has an aspect ratio of 4:3 and is a circle 150, an ellipse 150a to be a horizontally long video will be displayed in the displayed picture of the CRT 107 having an aspect ratio of 16:9 if the video signal is not compressed by the time axis compressing circuit 103 (see FIG. 4(a)).
However, it is possible for the horizontally long video mentioned above to be displayed in a normal video. That is, a video having an aspect ratio of 4:3 (e.g. the above circle 150) can be displayed in a picture display having an aspect ratio of 16:9 by compressing the displayed video shown in the FIG. 4(a) at a predetermined compressing rate from right and left.
That is to say, as the video of the current broadcast (NTSC) having an aspect ratio of 4:3 can be displayed in the displayed picture of the CRT 107 having an aspect ratio of 16:9 as mentioned above, the predetermined compressing rate will be: EQU (9/3).times.4/16=3/4.
That is to say, if the displayed video is compressed at a compressing rate of 3/4, a normal video of 4:3 can be displayed in the picture.
It is also well known that such video signal compressing process can be easily carried out using a digital signal and a digital processing circuit.
On the other hand, when the above video signal input is compressed at rate of 3/4 and displayed in the displayed picture of an aspect ratio of 16:9 (see FIG. 4 (b)), a part of no signal is produced on the right and/or left of the displayed picture of the CRT 107 as blank part 107a.
In order to effectively utilize blank part 107a and to restore the features of the wide aspect television, a function called a picture out picture function is used to display a son picture in the blank part 107a. That is, a function of a two pictures video is adopted.
FIG. 5 is a block diagram showing an example of wide aspect television provided with such two pictures video function.
As shown in FIG. 5, the video processing circuit group carrying out the two pictures video process comprises mostly a video processing circuit for displaying a parent/first picture (shown on the upper step in FIG. 5) and a video processing circuit for displaying a son/second picture (shown on the lower step in FIG. 5).
The video processing circuit shown on the lower step is generally a son picture video processing circuit for producing the second picture in the main first picture, for compressing the second picture video signal at a predetermined compressing rate, and for reproducing it as synchronized with the first picture.
The video processing circuit on the upper step is formed of substantially the same components as of the video processing circuit shown, for example, in FIG. 3. The difference is that a 1/2 compressing circuit 53 compressing the time axis at a compressing rate of 1/2 is provided and is characterized by being connected in parallel with a 3/4 compressing circuit 54.
In FIG. 5, reference numeral 50 represents an input terminal in which a broadcast signal of an NTSC system is to be input. The video signal input from this input terminal 50 is fed to a video signal processing circuit 51 formed of at least video intermediate frequency amplifying and video detecting circuits (not illustrated). It then is converted to an intermediate frequency signal, is taken out, and is separated into a luminance signal Y (which shall be abbreviated as a Y signal hereinafter) and a chroma signal. The chroma signal is demodulated to color difference signals (R-Y, B-Y).
The Y signal and color difference signals demodulated by the video processing circuit 51 are fed as analog signals to an A/D converting circuit 52 are converted to digital signals. The output signals of this A/D converting circuit 52 are fed to a time axis 1/2 compressing circuit 53 that compresses the input signals at a compressing rate of 1/2. The digital signals are compressed at a compressing rate of 1/2 are fed to the D/A converting circuit 55. Additionally, the output terminal of the A/D converting circuit 52 is connected to a time axis 3/4 compressing circuit 54 that compresses the time axis at a compressing rate of 3/4. The input digital signals compressed at a compressing rate of 3/4 are fed to the D/A converting circuit 55. The output signals of the 1/2 compressing circuit 53 and 3/4 compressing circuit 54 are switched by a switching means (not illustrated). For example, the picture having a 4:3 aspect ratio (NTSC) can be selected to be of a mode of displaying a picture having a 4:3 aspect ratio or of a mode of displaying two pictures. The switching means (not illustrated) is operated by a control signal from a controlling means (not illustrated).
The digital signals compressed by either the 1/2 compressing circuit 53 of 3/4 compressing circuit 54 are converted to analog signals by this converting circuit 55 and are fed to the video processing circuit 56. Thereafter, the video signal compressed in the time axis is video-processed by this video processing circuit 56 as in the ordinary television receiver. Additionally, the respectively color difference signals and Y signal are added to each other by using a matrix circuit 57 are, and fed to an adding means 58.
On the other hand, in the video processing circuit for displaying the son/second picture shown on the lower step, the video signal input from the two pictures video signal input terminal 59 is similarly processed, the digital signal of the second picture video is fed to a digital processing circuit 62 through a video processing circuit 60 and A/D converting circuit 61, and the fed signal temporarily memorized in a digital memory 63.
In the digital processing circuit 62, a clock pulse is produced from a synchronizing signals, for example, of the first picture and second picture. Also, signals are written into or read out of the digital memory 63 by the timing of this clock pulse. That is to say, they are read out by synchronizing the video signal of the second picture with the video signal of the first picture and 1/2 compressing and are subsequently output.
The output signal of the digital processing circuit 62 is converted to an analog signal from the digital signal by a D/A converting circuit 64. It is then fed to the adding means 58 through the video processing circuit 65 and RGB matrix circuit 66 in the manner mentioned above.
Therefore, when two pictures are displayed, the first picture video processing circuit 51 uses the 1/2 compressing circuit. The video signal compressed in the time axis at a 1/2 compressing rate in this 1/2 compressing circuit will be fed to the adding means 58. At the same time, the synchronization with the video signal of the first picture will lag by 1H/2 from the second picture video processing circuit 60, and the 1/2 compressed second video signal will fed to the adding means 58. The first video signal and second video signal will be added to each other by adding means 58, and this added synthetic video signal will drive CRT 67 having an aspect ratio of 16:9. Thereby, the two pictures video shown, for example, in FIG. 6(a) will be displayed in the CRT 67.
However, in this state, the displayed pictures obtained by dividing this displayed picture of 16:9 into two parts are shown in FIG. 6(a). That is, the first and second pictures having an aspect ratio of 8:9 will be displayed in the pictures of the CRT 67 having an aspect ratio of 16:9 so that vertically long videos will displayed.
Therefore, when a synchronous signal is detected by the video processing circuit 51 and adjusted in vertical amplitude by a deflecting means (not illustrated) on the basis of this synchronous signal, the video in such state will be made a normal video. That is, the first and second displayed pictures will be of an aspect ratio of 4:3. For example, when the vertical amplitude is compressed in size by 2/3, a two picture display is achieved as is shown in FIG. 6(b). That is, the first and second pictures having an aspect ratio of 4:3 can be displayed in the CRT 67.
However, even if the ordinary picture of an NTSC (4:3) or two pictures can be displayed in the CRT of an aspect ratio of 16:9 when the conventional wide aspect television provided with a two pictures video processing circuit, there will be a disadvantage that the two pictures will be able to be displayed by only the video signal of an aspect ratio of 4:3 of the NTSC system in the current broadcast. That is to say, there will be a problem that the two pictures formed of the video signal having an aspect ratio of 4:3 of the NTSC, etc. and the video signal having an aspect ratio of 16:9 as of the hi-vision broadcast, etc. will not be able to be displayed together without horizontal and/or vertical distortion.